A Pictorial Guide for the Identification of Mold ... - OAR@ICRISAT

Bipolaris spicifera (Bainier) Subram.
(Bipolaris species "with" Cochliobolus teleomorph)
Helminthosporium spiciferum (Bainier) Nicot
Helminthosporium tetramera McKinney
Curvularia spicifera (Bainier) Boedijn
Teleomorph. Cochliobolus spicifer Nelson
Symptoms on grain. Colony on seed is brown, gray or black, hairy, cottony or cushion-like
and spreads loosely with abundant brownish conidiophores, single or in clusters of 2-3
(Fig. 30). Many small conidia are produced at very short intervals, giving rise to a bottle-brush
appearance. Colonies strongly resemble those of Curvularia spp.
Morphology. Conidiophores are brown and curved, with obvious and numerous scars
resulting in an irregular zigzag appearance. Conidia are short, typically 3-septate, light to dark
brown, oval, curved to straight with rounded ends, and measure 20-40 μm x 9-14 μm. Conidia
are lighter in color towards the terminal cells.
Ascomata are black, spherical to oval, curved, 460-710 x 350-650 μm, with an inverted cone-
shaped neck and pore. Asci are cylindrical to club-shaped, straight to slightly curved, with 1-8
spores and 130-160 x 12-20 μm. Ascospores are parallel to closely coiled in the ascus, thread-
like, somewhat tapered at the ends, 6-16 septate, hyaline, and 135-240 x 3-7 μm
(Fig. 31).
Quick clue. Under the dissecting microscope, conidia appear to be clustered for some length
on the conidiophores, giving the appearance of a bottle-brush. Conidia are very small and
typically 3-septate, almost cylindrical, more or less uniform in size, and the end cells have
subhyaline areas towards their terminal ends.
Importance. Bipolaris spicifera is distributed worldwide and is very common in tropical and
subtropical areas. The mycotoxins isolated from B. spicifera are spiciferone A and cynodontin
metabolites and those from C. spicifera are curvularin and D-mannitol (Combe et al. 1968;
Nakajima et al. 1989). The main diseases caused by B. spicifera are foot rot (or common root
rot) of winter wheat (Triticum aestivum L.) and mycotic keratitis in humans. A subcutaneous
mycosis in cat and horses is also induced by C. spicifer.
36